When a disc drive is energized, it warms up and has a temperature rise. In particular, there are large temperature rises in the heads used in a disc drive. The heads include magnetic transducers deposited on slider substrates. The magnetic transducers carry electrical currents that generate heat in the heads. The temperature rise in the heads is large because the heads have a small surface area in relation to the amount of heat that is dissipated in the magnetic transducers.
The magnetic transducers typically have a higher coefficient of thermal expansion (CTE) than the slider substrates. As temperature increases, the magnetic transducers thermally expand at a greater rate than the slider substrates. The thermal expansion causes the pole/shield tips of the magnetic transducers to protrude with respect to an air bearing surface of the slider substrate. At higher temperatures, the pole/shield tips are closer to the media and the pole-to-disc spacing (also called transducer-media spacing or fly height) is reduced. If the pole-to-disc spacing at lower temperature is not large enough, the protruded pole/shield tips hit the media at higher temperature.
To avoid transducer-media contact at higher temperatures, the pole-to-disc spacing at lower temperatures is kept relatively large. This large pole-to-disc spacing at lower temperatures, however, undesirably limits the electrical performance of transducers, particularly the areal bit density (gigabits per square inch) that can be achieved.
A method and apparatus are needed that correct the problems associated with pole tip protrusion at higher temperatures.